1. Field of the Invention
The present invention relates to device discovery in a wireless system. More particularly, the present invention relates to a method and apparatus for managing device discovery in a wireless system.
2. Description of the Related Art
In recent years, mobile devices supporting Wireless Fidelity (WiFi) direct or WiFi Peer-To-Peer (P2P) are becoming more widely distributed and used. The WiFi direct is a communication standard for transmitting data between devices through WiFi communication systems. However, until now, Bluetooth and Digital Living Network Alliance (DLNA) systems have been primarily used for data sharing between devices. However, WiFi may enable wireless data exchange at a wider transmission range and faster speed than Bluetooth and DLNA systems.
Data transmission using WiFi direct does not require an Access Point (AP). WiFi direct connects devices directly without a separate AP. Accordingly, there is no need to access a WiFi zone or network. Furthermore, WiFi direct may connect devices on a point-to-point basis or on a point-to-multipoint basis, which may be referred to as a P2P group.
FIG. 1 depicts a P2P group that includes devices connected by WiFi P2P according to the related art. FIG. 2 is a communication flow diagram of general device discovery between devices according to the related art.
Referring to FIGS. 1 and 2, one device becomes a P2P group owner 101, and the remaining devices become P2P clients 102. The connection between devices illustrated in FIG. 1 precedes a process of detecting an existence of a peer device, which may also be referred to as a process of device discovery. A WiFi P2P device scans all channels through a scan method based on the Institute of Electrical and Electronics Engineers 802.11 network standard and finds a previously created group owner. When failing to discover the group owner from the scanning of all channels, the WiFi P2P device repeats the process of listening and searching, in which the WiFi P2P device is respectively in a listening state and a searching state. However, the process of listening and searching are repeated limitlessly, and the device discovery may end after a predetermined amount of time.
Similar to a process in which a WiFi P2P device detects the existence of an AP in an existing 802.11 network, a basic method in which a WiFi P2P device detects the existence of a peer device for WiFi P2P device discovery includes an exchange of a probe request message and a probe response message according to the IEEE 802.11 Media Access Control (MAC) protocol.
The WiFi P2P device sends the probe request message to a peer device and receives the probe response message from the peer device, thereby detecting the existence of the peer device. Also, the WiFi P2P device should permit being, i.e., be enabled to be, discovered by the peer device in response to a probe request message transmitted from the peer device. This being enabled to be discovered may be referred to as the listening state. The listening refers to a duration of time, or time interval, in which the WiFi P2P device enables its Reception (RX) part and monitors for a probe request message of the peer device. The searching refers to a duration of time, or time interval, in which the WiFi P2P device may send a probe request message to the peer device and receive a probe response message from the peer device. The WiFi P2P device, which is not a P2P group owner, performs the listening through one fixed channel from among channels 1, 6, and 11 of the IEEE 802.11 standard and performs the search through the channels 1, 6, and 11. As a result, two WiFi P2P devices may both repeatedly perform the searching and the listening and may simultaneously discover each other.
Furthermore, the WiFi P2P device may further perform service discovery through the searching. The service discovery includes a message exchange that is used for determining service information, such as a service protocol type of a peer device and the like. Although two WiFi P2P devices connect with each other, the connection of the two WiFi P2P devices is useless if their supporting service information are different from each other. For example, in a case where a first WiFi P2P device uses a Universal Plug and Play (UPnP) based file sharing scheme, while a second WiFi P2P device uses a Web service based file sharing scheme, file sharing between the two devices may be difficult.
According to the communication flow diagram of FIG. 2, the first WiFi P2P device 201 that is searching sends a probe request message to the second WiFi P2P device 202 through channel 6 at step 203, and the second WiFi P2P device 202 that is listening sends a probe response message to the first WiFi P2P device 201 through channel 6 at step 204. Through this message exchange, the first WiFi P2P device 201 detects the existence of the second WiFi P2P device 202. Furthermore, the first WiFi P2P device 201, being the searching device, and the second WiFi P2P device 202, being the listening device, may exchange service information through channel 6. Accordingly, a WiFi P2P device may detect information about a MAC address of a peer device, a network name (i.e., a Service Set IDentifier (SSID)), a device name, a device type, a service protocol, a service type, and other similar and suitable information.
FIG. 3 is a diagram illustrating a comparison of current consumption patterns of listening and searching according to the related art.
Referring to FIG. 3, the searching uses a time interval corresponding to a generating of a Transmission (TX) peak current for sending probe request messages to a peer device respectively on channels 1, 6, and 11, and uses a time interval for maintaining Reception (RX) current for receiving a probe response message from the peer device. Also, the listening uses the time interval for maintaining the RX current for receiving a probe request message from the peer device. Because the TX peak current corresponding to the sending of the probe request message is generated spontaneously, there is almost no difference of a consumption current between the listening state and the searching state, when executed during a same time interval. That is, the difference of the consumption current between the listening state and the searching state, during the same time interval, is proportional to a difference of the consumption current for respective durations of time allotted to the listening process and the searching process.
Although not searching for a specific peer device through the searching state, the WiFi P2P device may conduct only the listening state so that the peer device may be able to find itself. For example, when the peer device wants a connection, it is desirable that the WiFi P2P device, such as a printer having a WiFi function, a Television (TV), a facsimile, a speaker, and any other similar device, maintains a state of being discoverable by the peer device by maintaining only in order to increase a user's convenience. That is, in a situation in which the peer device may not know when to begin the device discovery process described with reference to FIG. 2, then it is reasonable that the WiFi P2P device maintains only the listening state and is in a state of being discoverable by the peer device.
However, the WiFi P2P device maintains only the listening state to indicate that the WiFi P2P device consumes the RX current continuously. Maintaining only the listening state in a situation in which the WiFi P2P device is not sure when the WiFi P2P device will receive a probe request message or a service discovery request from the peer device results in a waste of resources, such as battery life. That is, although the peer device does not perform a device discovery process, the WiFi P2P device maintains only the listening state, which is inefficient with respect to current consumption. However, the WiFi P2P device may execute a repeated periodic listening state and sleep state in order to decrease current consumption, but a probe message may be delayed in such a case because the WiFi P2P device may not respond to a probe request message of the peer device while in a sleep state. Also, a duration of listening and a period or time interval of listening may be shortened, but such goes against reducing the current consumption.
Therefore, a need exists for a system and method for performing a self diagnosis of a device without the inconvenience caused when manually selecting a self diagnosis item from a computer or a user interface.